iron-57 is a naturally occurring stable iron isotope that is present in all living organisms. It is commonly used as a tracer to measure iron absorption and loss in the body.
Stable 57Fe is an ideal tracer because it is readily available in natural iron compounds and has no decay products, making long-term monitoring possible. It is also a good indicator of dietary iron intake because it decreases when ingested but does not affect the concentration of iron in the body.
Characterization of 57Fe by Mossbauer spectroscopy
Fe-57 is studied using the recoilless gamma-ray emission and adsorption method of Mossbauer spectroscopy, named after Rudolph Mossbauer who first observed this phenomenon in 1957. This technique allows very precise information about the chemical, structural and magnetic properties of a material.
The 57Fe Mossbauer spectrum of dimeric DNIC-cysteine (Fe:Cys = 1:2) was characterized by an isomeric shift and quadrupole splitting values similar to those found in metallic Fe. In contrast, the 57Fe GR spectrum of Cys-DNICs treated with gaseous NO revealed a complicated shape that can be described by an increased radial order.
This is due to the fact that the 57Fe atomic spins are trapped in a HS state until the nucleogenic iron(II) complex turns into the LS ground state. As the ligand field strength is reduced, a higher intensity is exhibited by the 57Fe-HS resonances. These resonances are similar to those in a 57Fe-LS complex. The 57Fe-HS resonances are associated with the spin of the iron(II) nucleus which is influenced by its magnetic moment.